P.R. - my final word
I'm firmly entrenched in my opposition to PR, but Andrew Coyne's discussion has been excellent and intelligent. To wrap up, I think I'd like to set out my final objections, for evisceration by smarter folk than me.
For the sake of argument, and because it seems to be most favoured by supporters, let's say that the PR model being considered is 50/50 MMPR. 308 MPs would be elected, as now, via first-past-the-post in 308 ridings. An additional 308 MPs would be elected via affiliation with their party's percentage of the national popular vote (note - debate over the proper size of the House of Commons is for another day).
My overall objections to PR in all its forms are outlined in previous posts, as well as here and here. Let us consider the possible sub-models of 50/50 MMPR, i.e. how exactly the other 308 MPs should be chosen.
1) Ghost MPs
Skip the actual people; if Liberals win 115 PR MPs, the Liberal leader simply has 115 additional votes on every issue as well as his own. This is my favorite sub-model, because it's the most honest. If the Liberals gain the 115 MPs because of Liberal Party support, it should be the Liberal Party who makes the decisions. The sole objection here is that the optics are awful (and as such, is a pretty good argument against PR as a whole).
U.S. Electoral College! Same as 1), but have human beings raising their hands to vote, representing their party's views exactly. The identity of the Robo-MPs is unimportant, as they exist solely to vote the party line. Objection here is that it's dishonest; using figureheads to obscure the undemocratic stench of 1).
2) MPs appointed by the party off their own list. We already have a place where party hacks can while away their days with little fear of losing their jobs - the Senate. We also now approach the point where individual MPs may vote against the party line, undermining PR's stated purpose of party representation.
3) MPs appointed by the party based on internal elections. As I have noted, this poses a real conundrum when it comes to the stated purpose of PR. Voters are electing the party; yet there is a real likelihood that the people who "win" the internal party elections did so by differentiating themselves from party boilerplate. Single issue sub-groups within a party could no doubt elevate favoured candidates into very high positions on the party list. Rural western NDPers could absolutely get pro-lifers to near the top of their party list; is this what Toronto's NDP voters are supporting when they vote NDP?
4) MPs voted in directly off a list by their party's voters. All the problems of 3), with the added bonus of more difficult balloting. Intra-party campaigning would be going on at the same time as the general election, which would be chaos. Voters would need to weigh the merits of the party, as well as the merits of the individuals running, which should be noted is the exact same situation as we have now.
5) MPs to be "riding losers" with the biggest % of popular support. I hate this option, which would allow candidates rejected by voters in their own hometowns to slip in Parliament's backdoor. These people are probably least likely to toe the party line, because they're going to have to run again next time, and need to appeal to their home riding. Defeats the purpose, or at least diminishes the effectiveness, of PR.
There you have it. If I'm not right, at least I hope I'm clear.